with_output_buffer

# File actionview/lib/action_view/helpers/capture_helper.rb, line 221
      def with_output_buffer(buf = nil) # :nodoc:
        unless buf
          buf = ActionView::OutputBuffer.new
          if output_buffer && output_buffer.respond_to?(:encoding)
            buf.force_encoding(output_buffer.encoding)
          end
        end
        self.output_buffer, old_buffer = buf, output_buffer
        yield
        output_buffer
      ensure
        self.output_buffer = old_buffer
      end